doi:10.1038/nindia.2013.3 Published online 17 January 2013
Researchers have devised a new technique that could detect a specific toxin-producing gene of Streptococcus pyogenes, a bacterium known to cause rheumatic heart disease (RHD) in humans. This technique will be very useful in diagnosing RHD at an early stage.
RHD begins with throat infection and gradually affects the heart, joints and even brain. In recent years, S. pyogenes has grown resistant to antibiotics that prevent the bacteria from binding to host cells. As a result, the bacteria remain in patients for weeks and infect others. Early detection is necessary to initiate therapy and keep RHD at bay.
Existing blood tests are time-consuming and complex. To find a fast and accurate detection technique, the researchers have developed a polymerase chain reaction-based method relying on the streptococcal pyrogenic exotoxin B (SpeB) gene. This SpeB gene codes for a toxin that contributes to the virulence of S. pyogenes.
The researchers isolated bacterial DNA from patients' throat swab samples, used specific molecules to amplify the speB gene and made comparison with the speB gene of S. pyogenes genomic DNA isolated from similar cultured bacterial cells. Both genes were identical.
The speB gene does not show similarity with any other genes of other organisms, and so can be used as a genetic marker for early detection of S. pyogenes-induced RHD. The present method is simple, economical and fast, taking only 80 minutes to diagnose the disease.
"The speB genetic marker can be used in the hospitals for early diagnosis of RHD to prevent heart valve damage," says lead researcher A. Kumar.
The authors of this work are from: CSIR-Institute of Genomics and Integrative Biology, and National Centre for Disease Control, Delhi and Shoolini University of Biotechnology and Management Sciences, Himachal Pradesh, India.